The stapling instrument of the present invention can be used in any situation where the element to be stapled is approached from one side only and the staple is formed about an anvil, rather than against an anvil. The stapling instrument is particularly adapted for use as a surgical stapling instrument and will, for purposes of an exemplary showing, be so described. By proper selection of materials, the instrument may be manufactured as a reusable instrument. It construction is such, however, that the majority of its parts lend themselves well to be molded of plastic and the instrument can readily be produced as a single-use disposable instrument. For purposes of an exemplary showing, the instrument will be described in its application as a single-use, disposable surgical stapling instrument.
Surgeons have come more and more to the use of staples, rather than conventional thread sutures, for closing wounds or incisions in the skin and fascia of a patient. This is true primarily because the use of staples is a far easier procedure and, of even greater importance, is very much faster. The use of staples substantially reduces the time required for suturing and thus the length of time the patient must be maintained under anesthesia.
Prior art workers have developed various types of surgical stapling instruments, examples of which are taught in U.S. Pat. Nos. 3,618,842; 3,643,851; 3,717,294; 3,837,555 and 3,873,016. In general, the prior art instruments are complex in construction and expensive to manufacture. They do not lend themselves to a disposable construction. Prior art surgical staplers generally require a magazine or cartridge for the staples and a portion of the force required to actuate these instruments is expended in shifting a staple to an anvil means, prior to the formation of the staple about the anvil means. As a result, some prior art surgical staples require upwards of 20 pounds force to form and implant a surgical staple.
An important advance was made in the surgical stapling instrument art by U.S. Pat. Nos. 4,109,844 and 4,179,057. These references teach single-use, disposable instruments provided with an anvil plate by which the surgical staples are supported and along which they are fed. The anvil plate terminates in a coextensive anvil surface and means are provided, separate from the staple forming and implanting means, to constantly urge and advance the row of staples along the anvil plate to place a forwardmost staple of the row on the anvil surface to be formed by a staple driver. All of the force required to operate these surgical stapling instruments is directed to the forming and implanting of the forwardmost surgical staple and no part of the force exerted by the surgeon is required to shift a staple from a cartridge or magazine to the anvil surface about which it is formed.
The present invention provides a disposable surgical stapling instrument which represents an improvement over that of the above mentioned U.S. Pat. No. 4,179,057. The surgical stapling instrument of the present invention is characterized by all of the advantages of the surgical stapler taught in the above mentioned U.S. Pat. No. 4,179,057. In addition, the surgical stapling instrument of the present invention is characterized by an unique overall construction which is even simpler and requires fewer parts; a unique trigger and trigger-biasing means, an improved surgical staple magazine constituting an integral, one-piece part of the surgical stapling instrument body; and an improved anvil plate which narrows the opening through which the forwardmost surgical staple is formed. This latter advance accomplishes two things. First, the anvil plate fully supports the leg and crown portions of that staple adjacent the forwardmost staple of the row, as well as all of the staples therebehind. This assures that that staple immediately behind the forwardmost one of the row will be in proper position for forming when it becomes the forwardmost staple of the row. Secondly, with this second staple being fully suported, gives better support to the forwardmost staple of the row being formed, since it helps hold the forwardmost staple under the former and reduces possible leg roll during the forming procedure.